In Firefox, Safari and Chrome this gets an alert that says "success" almost immediately. In IE9, it gets a "failed" after a decent delay. You can see this example running on a live site with a CORS compatible URL here.
Has this definitely been tested and is definitely working?
The XDomainRequest object used by Microsoft doesn't have such an event. It's events are onerror, onload, onprogress and ontimeout as described here. THIS CODE COULD NEVER OF WORKED!
Is it any wonder that the current state of ExtJS 4 is in complete disarray. First you use Ext.isIe instead of Ext.isIE, then you are trying to bind to events that don't even EXIST!This is basic stuff! Just testing this code once will have shown this error. Seriously, JUST ONCE!
If there is code like this in such a core part of the framework that has not been run or tested then it begs the question what else is hiding in ExtJS 4? It begs an even bigger question of me - how was I tricked into paying for this.